1. Field of the Invention
This invention generally relates to novel alloys and methods of producing the alloys. More specifically, the alloys are high-strength nanostructured alloys.
2. Description of the Related Art
Basic research in the field of alloy materials seeks to find improved materials, such as those that are lighter, stronger, or less expensive to produce than conventional alloys. In other contexts, improved materials may have increased resistance to weather, chemicals, or friction, in an intended environment of use. Equipment that incorporates these new materials in component parts may have a longer service life, require less maintenance, or achieve an improved performance level. From a cost of manufacture standpoint, it is desirable for these new materials to be made from readily available and highly affordable natural resources.
One technique that may be used to produce an alloy with enhanced strength is spinodal decomposition. Spinodal decomposition processes are described, for example, in Ramanarayan and Abinandan, Spinodal decomposition in fine grained materials, Bltn. Matter. Sci. Vol. 26, No. 1, 189-192 (January 2003), and the transition phase kinetics of spinodal decomposition are described in Mainville et al., X-ray scattering Study of Early Stage Spinodal Decomposition in Al0.62Zn0.38, Phys. Review Lett. Vol. 78, No. 14, 2787-2790 (1977). The Toughmet™ Cu—Ni—Sn alloys that are commercially available from Brush Wellman of Lorain, Ohio are one example of spinodal alloys used for structural applications.
Spinodal Fe—Ni—Al (Alnico) systems were studied by S. M. Hao; K. Ishida; T. Nishizawa, “Role of Alloying Elements in Phase Decomposition in Alnico Magnet Alloys” Metall. Trans. A, 16(2), Feb. 1985, 179-185. To a base Fe—Ni—Al system a small amount (less than 5 at. %) of Cu, Ti, Mn, V, Cr, Si, Mo, or Nb was added. The microstructure, miscibility gap characteristics and magnetic properties of the resulting materials were determined. The authors concluded that the elements Mn, Nb, Cr, Mo, Si, and V were “estimated to be of little use in Alnico alloys” (p. 183, col. 2).
U.S. Patent Application Publication No. 2002/0124913 discloses another Alnico compound, Fe—Cr—Ni—Al, that resists oxidation and exhibits high strength. The alloy consists essentially of, by mass, 0.003 to 0.08% C, 0.03 to 2.0% Si, not more than 2.0% Mn, from 1.0 to 8.0% Ni, from 10.0 to 19.0% Cr, 1.5 to 8.0% Al, 0.05 to 1.0% Zr and the balance Fe. Under certain conditions, an intermetallic composition, e.g., Ni—Al, precipitates in the ferrite matrix as a non-spinodal second phase.
To date, very few spinodal Alnico systems are known, and the presence of Mn in those that are known is considered detrimental to the properties of the final product.